The subject invention relates to a plastic fastening element having an insert portion for attachment in an aperture of a support. Distributed over the outer circumference of the insert portion are elastic triangular wings that extend generally in the axial direction of the support aperture. A first side of each triangular wing is connected with a core of the insert portion with the opposite corner of the triangle defining the outer limit of the second and a third sides of the triangle that extend between the opposite corner and the core of the insert piece. A cap piece is connected with the upper region of the insert portion and functions to cover the support aperture.
A similar fastening element is known in the prior art (U.S. Pat. No. 5,454,479 corresponding to German PS 42 42 154) which is specifically designed as a cover lid. Such a cover lid serves, for example, for closing a collar hole in the body of a motor vehicle and has a generally dish-shaped top part. This prior fastening element includes a cylindrical jacket-shaped wall carrying wings designed as engagement elements. The wings extend over at least part of the exterior surface of the wall at an acute angle relative to the radial lines of the wall. The closing lid is retained within the collar hole with the aid of the wings.
Among the further state of the art, there is also a mounting attachment for a lamp holder (U.S. Pat. No. 5,037,326). The mounting has a cylindrically shaped wall with engagement elements in the form of obliquely arranged wings on the outer circumference of the wall. In this device, the wings have the function of holding the lamp holder within a cylindrical bore in that the outer surfaces of the wings are pressed against the inner circumference of the bore. Tolerance compensation with this known construction is not intended.
In contrast to the prior art discussed above, the object of the present invention, based on the initially described fastening element, comprises further refining the construction in such manner that with slight press-in force there is guaranteed improved mounting tolerance with respect to sheet metal thickness and the diameter of the support aperture.
The above task is solved according to the invention in that the second or lowermost triangle side of each wing descends from the radial outer corner of the respective wing in a spirally wound relationship relative to the core of the insert piece. Likewise, the third side of the wing ascends in a spirally wound relationship from the same outer corner to the core of the insert piece. Due to the special spiral shape of the wings, there is a resulting benefit allowing the fastening element to be simply pressed in simple fashion into an aperture of a support and embedded therein. Because of the special spiral design of the wings, different bores and sheet metal thicknesses can be covered with a single fastener size, so that inventory keeping is beneficially reduced.
By way of further refinement of the invention, there can be a space between the third side of the triangular wings and the underside of the cover piece, which space becomes smaller toward the core of the insert piece. As a result thereof, it is possible that, for example, greater sheet metal thicknesses of the support can be received between the top of the wing and the underside of the cover piece. This results in an expansion of the useful application range.
According to another feature of the invention, the cover piece can be equipped with a circumferential sealing lip which is inclined towards the insert portion. Also, the underside of the cover piece can have at least two radial cross-pieces that extend up to the core of the insert portion.
In addition, the wings can each have a chamfered or sloping portion at the lower end region, so that there will be improved functioning during installation. Inasmuch as the wings also have a sloping portion in the area of the third triangle side, this likewise affords a beneficial disassembly possibility.
According to a more limited aspect of the invention, a total of six wings may be arranged at the outer circumference of the core of the insert portion. Additionally, there is the possibility that there is a mounting and/or fastening area above the cover piece, so that due to the special design there will result a wide application range for the fastening element.
The invention is described in more detail, based on an exemplary embodiment represented in the drawing.
Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description.